There is increasing demand in the oil and gas industry for higher performance thermal coatings to insulate and protect off-shore transport conduits operating at temperatures of 130° C., or higher, in water depths above 1,000 meters. In order to maintain the conduit at the required operating temperatures at these depths, the coatings must have low thermal conductivity to prevent the formation of hydrates and waxes that would compromise pumping efficiency of the fluid in the conduit. The thermal conductivity can be further decreased through foaming the coating to some required degree. The materials used in this application must also exhibit high softening point, high thermal stability, and high compressive creep resistance in order to withstand the operating temperatures and hydrostatic pressures acting on the coating in deep water pipe installations. Without sufficient compressive strength, the insulation will be compressed in thickness, thereby increasing thermal conductivity and altering the dimensions and the thermal and hydrodynamic performance of the system. Also, it is important that the coating remain sufficiently ductile after application to the conduit to prevent cracking during pipe handling and installation, for example during reeling onto a lay barge and subsequent deployment therefrom.
Multi-phase fluid flow is common in subsea fluid transport conduits, such as flowlines and risers. Two main concerns in such systems are the formation of gas-water hydrates and the deposition of wax. Both of these phenomena are related to the temperature of the fluid, and in extreme cases the conduit can become severely constricted or even blocked. This in turn can lead to reduced or lost production. In particularly serious cases this may lead to the need to replace sections of pipeline or entire systems with corresponding loss of asset value. Thermal insulation is used to provide controlled energy loss from the system either in steady state condition or in the case of planned and un-planned stoppage and thereby provide a reliable basis for operation.
For single-pipe flowlines and risers, using bonded external insulation, the mechanical loads as well as the requirements placed on the mechanical and thermal performance of thermal insulation systems normally increase with water depth. Hence, the traditional thermal insulation foam technology used in shallow waters and the associated design and test methodologies may not be applicable to deep-water projects. In cases of long pipe tiebacks, for example subsea-to-beach tiebacks, and in cases where the service temperature is above approximately 150° C., there exist limitations with current technology that may hinder the successful development of offshore, deep water oil or gas fields.
Current technologies include single pipe solutions, typically with insulation requirements in the heat transfer coefficient range of 3-5 W/m2K, using polypropylene foam or polyurethane foam as the insulant, and so-called pipe-in-pipe systems wherein a second pipe surrounds the primary conduit, the annulus between the two pipes being filled with an insulating material.
Limitations and deficiencies of these technologies include:                Relatively high thermal conductivity of known insulating systems, necessitating excessively thick coatings to achieve the required insulation performance, leading to potential difficulties in foam processing, potential issues with residual stress, difficulties during pipe deployment, and sea-bed instability.        Insufficient resistance to temperatures above 130° C., resulting in compression and creep resistance issues in high temperature installations at high water depths.        Excessive costs due to poor material cost versus performance capabilities or high transportation and deployment costs.        Deployment and operation disadvantages with Pipe-In-Pipe systems due to weight factors leading to buckling and weld failure if not properly addressed, and the need for high gripping loads during pipe laying.        
Although the polystyrene-based insulation systems disclosed in International Publication No. WO 2009/079784 A1 by Jackson et al. (incorporated herein by reference in its entirety) provide improved thermal performance over known insulation systems at operating temperatures up to about 100° C., these polystyrene-based systems generally have insufficient resistance to temperatures above 130° C.
Therefore, there remains a need for improved coatings for thermal insulation and protection of fluid and/or gas transport conduits such as oil and gas pipelines, particularly those operating at high temperatures in excess of 130° C. in water depths above 1,000 meters.